Hi Ken,

I’d prefer that TF-M keep exporting the pre-compiled archive for regression tests. The rational behind that is less files to be added/maintained by NS RTOS.

Considering this, I think quick and easy way to solve this is for NS RTOS to implement ` tfm_log_printf ` using the print method available. This way no changes are needed in TF-M.

I thought about platform-specific shim layer, like adding a new print function “ns_log_printf” to the OS wrapper (app/os_wrapper_cmsis_rtos_v2.c) and use that for NS regression tests. I believe it’s not worth the effort and also it will add another layer of indirection.

To summarise, we’ll implement `tfm_log_printf ` in Mbed OS which should resolve the linker issue.

Thanks,

Dev

From: TF-M <tf-m-bounces@lists.trustedfirmware.org> on behalf of Ken Liu via TF-M <tf-m@lists.trustedfirmware.org>
Reply to: Ken Liu <Ken.Liu@arm.com>
Date: Wednesday, 5 February 2020 at 04:50
To: "tf-m@lists.trustedfirmware.org" <tf-m@lists.trustedfirmware.org>
Cc: nd <nd@arm.com>
Subject: Re: [TF-M] TF-M NS regression tests - linker issue

Hi Devaraj,

Thanks for the clarification. Looks like this issue is caused by the way the building system integrates the test package with NS RTOS - if source-level integration is applied then the modification is not a problem and this should be the better way - even if we recover the 'printf' implementation, for those RTOS who has no printf, it would be another issue.

I think the possible solutions can be:

If we keep using the pre-compiled archive, then some platform-specific shim layer needs to be available to provide platform-specific functions.

If we changed to source-level integration then things would be easier.

A quick way is as you requested, recover back to 'printf'.

For the 3rd point, there are some pre-actions to be done:

Make sure the compiler optimization function is limited for easier the implementation of these stdio functions. There is a leading patch for this: https://review.trustedfirmware.org/c/trusted-firmware-m/+/3217
Define the HAL functions for output so that the printf implementation is not CMSIS specific.

May I ask how you fix this issue?

/Ken

From: Devaraj Ranganna <Devaraj.Ranganna@arm.com>
Sent: Tuesday, February 4, 2020 11:16 PM
To: Ken Liu <Ken.Liu@arm.com>; tf-m@lists.trustedfirmware.org <tf-m@lists.trustedfirmware.org>
Cc: nd <nd@arm.com>
Subject: Re: [TF-M] TF-M NS regression tests - linker issue

Hi Ken,

Currently, TF-M build process creates an pre-compiled archive of NS tests and exports it. But the implementation of `tfm_log_printf` is not exported. This causes a linker issue when NS tests archive is linked with NS RTOS, which is the reason why subject of this mail contains `linker issue`.

Having said that, exporting `tfm_log_printf` won’t solve the problem because `tfm_log_printf` assumes availability of CMSIS driver framework.

Also the latest suggestion on the ticket https://developer.trustedfirmware.org/T664 `And I think if you forward the TEST_LOG to your OS printf implementation then everything would be fine?` won’t help because of pre-compiled archive.

It looks like only possible solution for NS RTOS is to implement ` tfm_log_printf `. Please do recommend if you have any other ideas.

Thanks,

Dev

From: TF-M <tf-m-bounces@lists.trustedfirmware.org> on behalf of Ken Liu via TF-M <tf-m@lists.trustedfirmware.org>
Reply to: Ken Liu <Ken.Liu@arm.com>
Date: Saturday, 1 February 2020 at 04:46
To: "tf-m@lists.trustedfirmware.org" <tf-m@lists.trustedfirmware.org>
Cc: nd <nd@arm.com>
Subject: Re: [TF-M] TF-M NS regression tests - linker issue

Hi,

Why the title is ‘linker issue’ since it is discussing about the printf things?

/Ken

From: TF-M <tf-m-bounces@lists.trustedfirmware.org> On Behalf Of Devaraj Ranganna via TF-M
Sent: Friday, January 31, 2020 9:57 PM
To: TF-M@lists.trustedfirmware.org
Subject: [TF-M] TF-M NS regression tests - linker issue

Hi,

The TF-M NS regression tests were portable enough to run in a rich OS environment. After replacing printf with tfm_log_printf, the TF-M regression tests are now no longer portable enough to run in an OS environment. Many OSes already have a way to print, usually via a printf function, and the TF-M regression tests probably should use this.

It's important that TF-M regression tests remain portable and capable of running in an OS environment so that system integrators can be confident that TF-M is working as intended post-integration.

I’ve already created a ticket for this https://developer.trustedfirmware.org/T664

Response from Ken in the ticket:

Hi Jamie,

The background for this changing is, the ARMCLANG printf involves \_\_stdout' into the image and this conflicts with some CMSIS functionalities. (CMSIS team reported that __stdout would affect the mutex init in ARMCLANG). That is the reason why I skipped the default printf.

I think for an RTOS, the toolchain provided printf sometimes come with unknown symbols and causes unexpected behaviour, as the discussion in list/channel, most people are trying to avoid toolchain printf and use some lightweight output.

And for the test, it should use wrapped TEST_LOG(), instead of calling printf itself, since some RTOS do not provide a std 'printf' function.

Is there any discussion thread about this issue?

Thanks

Thanks,

Dev

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